1. Field of the Invention
This invention relates to a container opener having a rotationally driven turntable for imparting relative rotation between the container and the lid and, more particularly, to such a container opener additionally having an axial drive moving a lid engaging structure into contact with the lid.
2. Summary of the Background Art
The patent literature includes a number of descriptions of jar openers including rotationally driven turntables/. For example U.S. Pat. Nos. 6,293,170 and 7,024,963 describe jar openers in which a lid engaging, non-rotating structure is manually moved and held down against the lid of a jar resting on a rotationally driven turntable. In the apparatus of U.S. Pat. No. 6,293,170, the action of depressing the lid closes an electrical circuit to turn on a motor driving the turntable, while releasing the lid breaks this circuit to turn the motor off. In the apparatus of U.S. Pat. No. 7,024,965, manually rotating a wheel at each end of a shaft extending across the top of the lid engaging structure moves the structure downward against the jar lid by means of a pair of gears attached to the shaft and engaging racks formed within the vertical guide shafts on which the lid engaging structure slides.
Other jar opening devices include an axial drive, moving the non-rotating lid engaging structure downward against the lid. In such devices, a mechanism must be provided for disengaging the axial drive after the lid has been engaged, or, at least after the lid is unscrewed. For example, U.S. Pat. No. 5,271,296 in which the axial drive brings the lid engaging structure into engagement with the lid and then slips to permit the cap to be removed from the container, with the slippage occurring in a slip clutch through which lead screws are driven to form the axial drive. Then, a control unit sensing a torque created by the relative rotation between the lid and the lid engaging structure cause the rotational drive, which rotates both the lead screws and the turntable turning the jar, to reverse its direction of movement, moving the lid engaging structure and the lid away from the jar.
A potential problem associated with using variations in the level of torque required to cause relative rotation between the lid and the jar arises from the fact that substantial variations in the torque levels required must be expected to occur between a jar having a small lid that has been unscrewed many times before and a jar having a large lid that has never been unscrewed before. Thus, what is needed is an automatic mechanism for disengaging the axial drive without relying on measurements of the torque required to cause relative rotation between the lid and the jar.